ANAN 200D - P2 - distorted audio

[la6gh]

Hi,
I just installed P2 on my ANAN 200D and tried it with SDRC without luck.
Everything looks OK except the audio which is terribly distorted. Also.
signals look more like AM ? (Thetis works fine...)

What have I missed??

73 de LA6gh
Nils

[Max]

Hi,
I just installed P2 on my ANAN 200D and tried it with SDRC without luck.
Everything looks OK except the audio which is terribly distorted. Also.
signals look more like AM ? (Thetis works fine...)

What have I missed??

73 de LA6gh
Nils

Please attach screenshot. Do not crop or edit.

https://www.sdr-radio.com/screenshot

Home tab selected in ribbon bar and RX DSP active and docked on left side. We may be able to see something.

73

Max

[la6gh]

Max,
Thanks for your response.
Hope the attached is what you mean/need,

73 de Nils

[KA1GJU]

Taking your image and zooming in I see QRM streaks ~27kHz apart. My reasoning is the even spacing and the slow reduction in signal strength as you go higher in frequency (Red arrows). If you zoomed out and went down in frequency, you will probably see the opposite if looking far enough down. Also, the sudden change in width as noted in the red box I drew on the bottom.

I'd say it's a switching power supply or an "SPS" as they call them. They tend to populate 75/80m band and very slowly drift up or down in frequency. There are some SPS's for amateur radio that are complete garbage when used on HF , the Powerwerx Switching Power Supply Model SS-30DV is one! Could be a desktop SPS (or laptop) going bad too. Start powering down equipment and watching the scope. Hopefully it's not the PC running the ANNAN 200D.

See attachment!

[Max]

Max,
Thanks for your response.
Hope the attached is what you mean/need,

73 de Nils

Hi Nils

I agree with Kriss. Pretty much all I am seeing on that screengrab is some quite nasty harmonics of something at even spacings (a local noisy switched mode PSU or charger of some sort?), one of which you are tuned to at 3532kHz. I only see three ham radio signals. There's a clearly visible LSB signal around 3748kHz. Possible faint CW at 3550kHz and of course the usual FT8 at 3573kHz. Other than that I don't see any meaningful ham radio activity.

When you say Thetis works fine, did you try both SDRC and Thetis at same the time this screenshot was taken and found plenty of activity on Thetis? If so that does seem very odd?

One thing that can cause horrible distortion that is not always obvious (does not show in the waterfall) is the RX DSP AGC panel if it is accidnetally (or intentionally) in OFF/Manual mode. You have not been able to show the RX DSP AGC panel in the screengrab (low resolution monitor?) If you have AGC OFF/Manual, then it's very easy to overload the DSP chain with an incorrect setting of the manual GAIN slider in the AGC panel. Make sure you have AGC turned ON...... I always use SLOW:

AGC.gif (15.51 KiB) Viewed 25793 times

73

Max

[KA1GJU]

To follow up on Max's comments, when I hear 'real' distortion it's usually the NB (noise blanker) on while RXing strong signals. Or too agressive NB or NR settings.
Personally, I normally don't use NB, NR, or even AN (auto notch). I hate listening to the warbling or under water sounding audio they can provide. I'm lucky to live
in a rural area, and am constantly hiunting down RFI and killing it at the soiurce versus covering it up.
JMHO

[jdow]

Looking at his picture I'd LOVE to be able to see his gain settings. That is a nice picture of an overloaded amplifier with its IMD terms showing. Gain settings are probably WAY WAY WAY too high. (Forget any idea of calibration. It ain't gonna happen. Set Video Gain to 0. The way Simon implements it that is the only good setting for it. That's one HUGE piece of grisly bone I have to pick with SDRC. All it SHOULD do is apply as a scale factor when painting numbers on the screen. Otherwise it risks overloading the DSP itself.)

(Gee, Joanne, he MIGHT be receiving a squarewave..... be nice.)

Naw, I feel grrumpy - nursing Loren's repaired rotator cuff..... Being nice is too much work.

{*_*}

[Max]

Looking at his picture I'd LOVE to be able to see his gain settings. That is a nice picture of an overloaded amplifier with its IMD terms showing. Gain settings are probably WAY WAY WAY too high. (Forget any idea of calibration. It ain't gonna happen. Set Video Gain to 0.

Ah, I knew something was missing on that screengrab. Just realised (slow or what?) that the Ribbon Bar is minimised. Also do not know where the gain settings for Anan live on the screen and what gain settings there are? There may only be LNA like on Hermes Lite 2? If HL2 is anything to go by, the LNA has to be WAY off to cause issues.

Regarding Visual Gain, personally the way I set this is to unplug the antenna then set the Visual Gain to place the RX noise floor on the base zero line (S0 or -130dBm) then connect the antenna again. Nils, as Joanne points out, in SDRC the Visual Gain setting does affect the received signal DSP chain so needs to be set somewhere near correct using my method or something similar. We can't see on the screengrab where the noise floor is as we are only seeing from about S4 up but it looks to be somewhere near correct.

Max

[Max]

Personally, I normally don't use NB, NR, or even AN (auto notch). I hate listening to the warbling or under water sounding audio they can provide.

Yes, me neither Kriss. The only NR I ever really use is NR5. On some signals this can be truly impressive. The other NRs I find either they need winding back a long way to make them listenable to until they produce almost no effect or they produce that dreaded burble. I'd rather listen to background noise compared to that!

Never used NB ever. People forever talk about using noise blankers (since way before SDRs) but I've never used one in an analogue RX either. I'm never really sure what they help with. The old Woodpecker perhaps? As far as passing cars with traditional ignition systems, they were only ever very transient (excuse the pun) and AFAIK that all went away decades ago did it not?

I do use the notch sometimes, if someone plants a carrier right in the middle of an SSB signal. For AM, constant tones can usually be eliminated with ECSS-L or U.

Like you Kriss, lucky to live in a rural area but painfully aware it only takes one neighbour half a mile away with trashy car battery charger or poorly installed solar array to ruin everything so I nervously await any extra noise cropping up. Probably worst I have at the moment is occasional use of an electric fence which I can live with. Mostly any RFI comes from my own house!

Max

[jdow]

Max, "Regarding Visual Gain", I discovered the DSP issue by trying to get the wrong piece of hardware properly calibrated using the Visual Gain control. It went extremely wonky before I could achieve calibration. I am not sure what feature in the system went bad. All the DSP should float nicely since it uses "float", 32 bit floating point numbers. And as I typed that I thought of settings for noise reduction, agc, and possibly the overload blanking. They do shift nicely with the way Simon gets visual gain by multiplying all samples by a visual gain "constant". Simon should probably look into that.

{^_^} (I just passed it along to Simon.)